Friction-type draft gear assemblies are widely used in the railroad industry to provide protection to a railway car by absorbing shocks in both draft and buff conditions. They are installed in alignment with a railway car center sill having a pair of front stops and a pair of opposed rear stops that form a draft gear pocket. It is well known that various railroads now use a standard draft gear pocket of 24.62 inches in length. As a result, it has been mandated that friction-type draft gear assemblies of different designs must fit into such standard draft gear pocket.
It has been further mandated and accepted to provide a standard friction-type draft gear assembly for use with a 24.62 inch long pocket which is capable of 3.25 inch travel in buff and draft directions.
Such friction-type draft gears are installed in combination with a separate yoke and include a housing having an open front portion disposed adjacent a pair of front stops and a closed rear portion which engages a pair of rear stops. A compressible cushioning element is positioned within the rear portion of the housing. A friction cushioning element is disposed in the front portion of the housing.
The friction-type draft gears further includes a spring release mechanism for continuously urging the friction cushioning element outwardly from the compressible cushioning element thereby releasing such friction cushioning element after compression of such draft gears. The compressible cushioning element is typically either of an all coil spring configuration as taught in U.S. Pat. Nos. 5,152,409 and 5,590,797 or of a coil spring and hydraulic assembly combination as taught in U.S. Pat. No. 3,368,698.
Related patent applications teach another type of friction draft gear assembly that incorporates the yoke as an integral portion of the housing at the open end thereof.
The friction-type draft gear assembly with an integrated yoke has an advantage in that it fits into a smaller pocket and its adjacent areas in the freight railway car, or provides for a higher shock absorbing capacity and longer travel when installed into a standard 24.625 inch long pocket.
However, as it has been discovered in some applications, a major drawback of the friction-type draft gear assembly with the integrated yoke is that it will only accept a main coil spring of a smaller diameter as installation of such spring through the open yoke end is prevented by the opening in such yoke end, which is smaller than the diameter of the main coil spring. As is well known, the size of the opening is selected to cooperate with the coupler arm disposed therein and provides for a predetermined clearance therewith.
Such arrangement enables the coupler arm to move during motion of the railway car around a curve but does not enable the coupler arm to tilt thus imparting unwanted bending stresses onto a key connection of the coupler arm with the yoke. The bending stresses are particularly undesirable when the key is vertically disposed.
Therefore, it has been necessary to maintain the size of the yoke opening smaller than the size of the standard coil spring. Such smaller diameter of the coil spring, as was discovered, reduces an overall performance of the friction-type draft gear assembly with the integrated yoke as compared with a similar friction-type draft gear assembly without the integrated yoke. Attempts to compensate for such performance reduction by increasing the length of the coil spring did not achieve a desired result, as the overall performance was not sufficiently increased.
Therefore, it is desirable to provide a friction-type draft gear assembly with the integrated yoke incorporating the standard coil spring and achieving a higher shock absorbing capacity.